Flexible tubes formed by spirally winding a wire are also known as flexible pipes, and have a variety of shapes and sizes. The flexible tubes are widely used for piping, joints, and as protecting tubes or underground pipes. The flexible tubes include interlock flexible tubes having capabilities of retaining the bending shape thereof, and semi-interlock flexible tubes having better resistance to lateral pressure as well as to torsion and tension.
The interlock flexible tube has a packing inserted into interlocking parts of adjoining wires as disclosed in FIG. 19(a) of Japanese Patent Application Publication No. 2002-243065 (Patent Document 1). The inserted packing prevents water leakage while water directly flows through the tube. Thus, the interlock flexible tubes are employed for water heaters, water discharge tubes of water purifiers, and faucets.
In contrast, the semi-interlock flexible tubes have no packing but have adjoining wires firmly interlocking with each other as disclosed in FIG. 19(b) of Patent Document 1. The semi-interlock flexible tube has an inner tube (e.g., a water flow tube) inside it, and is used as, for example, a shower hose.
In addition to the aforementioned flexible tubes, there has been known flexible tubes with an ellipsoidal cross-section for automotive exhaust pipes that require high heat resistance to high-temperature exhaust gasses as disclosed in Japanese Patent Application Publication No. 11-22456 (Patent Document 2).